There is a demand for a thinner digital camera to be mounted on a smartphone or the like. Examples of the technique for realizing this type of thinner digital camera include a technique that obtains an object image without using a lens (see, for example, Patent Document 1).
This technique obtains an image of an external object by attaching a special diffraction grating substrate to an image sensor and obtaining an incident angle of incident light by the inverse problem calculation on the basis of a projection pattern generated on the image sensor by light transmitted through the diffraction grating substrate.